I agree with KathyAire, some things just must be seen for the minds eye to 'get it'.
Have you seen this video:
http://www.youtube.com/watch?v=wprg5...eature=related
This video by Leah Day saved me from the binding beast.
My theory is 'the width of our binding controls how far from the corner we need to stop sewing before we turn our binding up to make the L and start sewing down the next side (edge).
It worked perfectly on a previous quilt then I was binding this past week and just couldn't 'get' that mitred, square corner. I picked my stitches back, folded the binding up, then back down even with the edge of the quilt and kept sliding the binding it until I had what I needed. I realized I was sewing to close to the edge before snipping my threads and folding the binding
up, then back down even with edge of the quilt.
I hope the video helps. I apologize I can't explain it any better. Best of luck.
This is the post that introduced me to the video.
http://www.quiltingboard.com/t-50217-1.htm